L. H.. HYMAN. 



be induced in Planaria by carbon dioxide is limited and does not 

 exceed 50 per cent, as long as the oxygen supply remains ample. 

 If the oxygen supply is reduced, although not to a point where 

 the respiration rate would be affected under ordinary conditions, 



50 

 45 

 40 

 35 

 30 

 25 

 20 

 15 



10 



5 



& 



8.0 7.5 7.0 6.5 6.0 5.5 5.0 4.5 



2 



FIG. 2. Graph of the amount of carbon dioxide liberated in the well water 

 by various acids. Amount of carbon dioxide in cc. per liter on the ordinate, pH 

 on the abscissa. The amount of carbon dioxide gas required to produce a given 

 pH is also shown. 



the oxygen consumption can be nearly abolished if the water is 

 saturated or nearly so with carbon dioxide. A carbon dioxide 

 content of 30 cc. per liter appears to yield the maximum de- 

 pressing effect, about 50 per cent., that can be obtained with 

 carbon dioxide, w T hen the oxygen supply is adequate. 



